Radiation therapy is used to treat various malignant tumors, either pre-operatively, as adjuvant therapy after surgery, as primary therapy for patients unable to tolerate surgery, or to treat recurrences after surgery. It has been demonstrated in many areas of surgical oncology that adjuvant radiation treatment following tumor resection reduces the likelihood of recurrence of cancer or other proliferative disease. Patients undergoing radiation therapy may receive external beam treatment, brachytherapy, or both.
Brachytherapy is a term used to describe the short distance treatment of cancer with radiation. This type of treatment typically involves placing the radiation directly into or near the tissue to be treated. The radiation dose may then be delivered over a short period of time (temporary implants) or over the lifetime of the source to a complete decay (permanent implants). Treatment is often delivered in fractions spaced in time to take advantage of the fact that normal cells recover from radiation exposure whereas diseased cells do not.
Brachytherapy may be divided into two main classes: intracavitary and interstitial. With intracavitary brachytherapy, the radiation sources are placed within a body cavity close to the affected tissue. In interstitial brachytherapy, the radiation sources are implanted within a volume of tissue. Positioning of the radiation sources is an important aspect of brachytherapy. In order to effectively deliver radiation to the target tissue while helping to minimize exposure (and radiation damage) of surrounding healthy or normal tissue, the radiation sources must be properly positioned during the entire course of treatment.
In early brachytherapy applications, fluid media comprising radioisotopes were used to fill a balloon positioned within a body cavity or organ in order to provide therapeutic radiation. Later it was recognized that spacing the radiation source away from the tissues being treated provided means to deliver the prescribed radiation with reduced likelihood of overdosing normal tissue. This led to filling the balloon with an attenuating medium, often saline solution, and then adding catheters within the balloon in order to position solid isotope sources. Traditional sources are isotopic seeds of, e.g., iridium 192, that are positioned on wires, and which are manipulated within the catheters to deliver the prescribed treatment to the target tissue surrounding the balloon and the treatment cavity.
Conventional applicators typically used for delivery of radiation therapy from within the vagina are generally rigid tubular cylinders that allow transmission of radiation. For example, an exemplary gynecological applicator is the Fletcher-Suit cervical applicator. This applicator consists of a central tube (tandem) and lateral capsules (ovoids or colpostats). The lateral colpostats provide intravaginal positioning while the central tandem traverses the vaginal canal to project into the cervix. Although the Fletcher-Suit applicator has been widely used, maintaining its position in situ can be difficult due to their weight and the difficulty of ensuring a secure connection between the colpostats and tandem. Other brachytherapy applicators have been developed, e.g., the Miami Vaginal Applicator (Nucletron BV, Veenendaal, NL). However, they can be uncomfortable and/or difficult to insert due to their rigidity and incapability of accommodating variations in anatomy, e.g., variations in the size, shape, and orientation of the uterus among patients, or postoperative distortions in anatomy. In addition, the metallic components of these applicators render them poorly suited for CT imaging and subsequent 3D dose planning.
Given the importance of brachytherapy in the treatment of gynecological cancer, brachytherapy applicators having physical and/or functional characteristics that help optimize radiation delivery to target tissues while minimizing exposure to healthy or normal tissues would be useful. Applicators that can be easily and securely positioned within the body would be desirable. Applicators that have multiple source lumens virtually artifact-free under CT imaging that would facilitate 3D dose planning would also be desirable. Additional applicator designs, e.g., applicators capable of being better tailored to gynecological anatomy would also be useful.